1. Field of the Invention
This invention relates to a sorting conveyor system of the kind using an automatic aligning and feeding device for sorting articles to be classified by size, weight, etc. including agricultural products such as fruits in large quantity per unit time and more particularly to a sorting conveyor system which is adapted for conveying such articles by feeding them in alignment with random spacing in the travelling direction thereof and is capable of sorting and discharging the articles even at a high conveying speed.
2. Description of the Prior Art
Sorting systems of the kind using a fruit sorting conveyor for conveying fruit thereon by aligning them with random spacing between one piece and another of the fruit and using varied kinds of measuring instruments for sorting them by appearance or size of the fruit at a certain point of the path of the conveyor have been put in practice. Such sorting systems of the prior art include the systems disclosed in Japanese Patent Publication No. Sho 52-20388, Japanese Laid-Open Utility Model Application No. Sho 53-29361, Japanese Laid-Open Patent Application No. Sho 53-136864 and Japanese Laid-Open Utility Model Application No. Sho 54-13854. In these prior art sorting systems, the article to be sorted, such as fruit, is sorted by classes on the surface of a conveyor and is discharged therefrom by means of an air jet using an air nozzle in combination with a solenoid valve in such a manner as to blow and drop the sorted fruit off one side of the conveyor.
An advantage of the above described arrangement to discharge the sorted article by an air jet is that the article is discharged from the surface of the conveyor without being touched. However, since the articles are dropped with strong air pressure applied thereto, they drop with an additional force applied thereto to accelerate their dropping speed. It is, therefore, a disadvantage of this arrangement that the impact of the sorted articles at the time of dropping becomes greater than the natural dropping impact. This is a serious drawback where the article to be sorted or classified is vulnerable to impacts, such as in the case of fruits or the like. Further, a typical fruit sorting facility wherein citrus fruits are sorted at a rate of 10 to 15 tons per hour uses a large number of air nozzles such as 90 to 100 air nozzles. These air nozzles are operated on 2000 to 2500 pieces of fruits per minute thus consuming a great amount of air. This necessitates use of a large compressor (45 KW or thereabout for example). Besides, each combination of the nozzle and solenoid valve momentarily operates (for about 1/10 second) to produce a loud sound of the air jet at a rate proportional to the above stated number of pieces of the fruit. This results in a noise that is hardly bearable by the workers. In addition to that, the arrangement is not economical because of the large amount of power consumed.
Further, there are other known automatic sorting conveyor systems of the kind having a conveyor arranged to convey articles and to sort them at a part of the conveying path of the conveyor. The details of these systems are as described in a monthly magazine called "AUTOMATION", Vol. 25, No. 14, pages 88-93, published December 1980 by NIKKAN KOGYO SHINBUN-SHA (Industrial Daily Newspaper Co.).
With respect to the sorting conveyor systems of other kinds, some systems of the type known as the slat conveyor type have been disclosed in Japanese Patent Publication No. Sho 45-21774 and Japanese Utility Model Publication No. Sho 46-15126. In addition, sorting conveyor systems of the type known as the tray type have been disclosed in Japanese Laid-Open Patent Application No. Sho 47-9871, Japanese Laid-Open Utility Model Application No. Sho 48-66288, etc. These conveyor systems of the prior art are adapted for sorting products at distribution facilities and are suited for handling relatively large and heavy articles. They require an excessively complex arrangement and excessively large space for handling relatively small, light-weight articles and cannot be readily installed within a limited space.
Another shortcoming of the prior art conveyor systems of the above stated slat or tray type is that the conveyor chain is disposed below the middle part of the slats or trays and this causes the machine oil which is applied to the chain and filth which results from the oil to soil the slats or trays. Therefore, these conveyor systems are hardly suited for handling such articles as foodstuffs, etc. that must be prevented from being soiled from a hygienic point of view.
A further shortcoming of these prior art conveyor systems is that the tiltable angle of the slats or trays is limited as they are arranged to be tilted to the left or right on a fulcrum which is disposed below the middle parts of them and thus cannot be tilted to a sufficient extent such as 70 to 90 degrees from their horizontal positions. Therefore, they are incapable of discharging such articles that have sticky lower surfaces or are not readily slidable.
It is a still further drawback of these prior art conveyor systems that, since their structural arrangement limits the possible extent of reduction in size of the slats or trays, the width of slat-like carrying or receiving plates or trays which are transversely arranged relative to the travelling direction of the conveyor cannot be sufficiently reduced, for example, to several cm or to a width between 1 and 5 cm (1/2 to 2 inches). This is because reduction of width to such a sufficient extent for sorting small articles would result in excessively large spacing between adjacent slat-like receiving plates or trays for carrying small articles. Further, for conveying and sorting small articles, they must be fed at fixed intervals to prevent more than one piece from being put on the same slat or tray. Therefore, it is impossible to feed the articles at random intervals.